I have no problem at all serving soda at 30-35 psi through 30' of line (3/16" beer line). I've done it for years and years.

But if you have to turn off the gas to serve, you may have some foam. I'd try it and see before hauling it to a party. Just see if you can serve it at 12 psi for a few, and if it works out then you're all se.

I have had it work well sometimes, and be very problematic other times- depending on which keg, shank, faucet, line, QD, etc. combination was used. I am going to try switching to a barbed QD and see if that helps.

You may have had the magic setup. I believe you are using barrier line now. Are you still only using 30 feet of that at 30-35psi?

I still stick to the advice of using a shorter larger line when bleeding the pressure for short term serving. Run the lowest pressure to get the flow you need. If you have ever tried to dial in a jockey box, the issues are very similar. Some resort to bleeding pressure, instead of keeping the pressure at the proper setting, and everything chilled to appropriate temps.

Line restrictions and such can have a serious impact on foaming. I tracked down one foaming issue to using one of those flare-to-sanke coupler adapters on a shank. The inner shape of those things don't work as well when reversed.

My cider, and some root beers, have had more foaming issues than ginger ale. That may be part of my troubles as well. Although, based on the number of threads about trying to get sodas to serve properly, I think it is a pretty common problem

I cab my root beer at 25psi for a week and serve it weekly at a farmers market where I make root beer floats. I server it @ 10psi with about 4-5 feet of hose. Comes out perfect with a beautiful head. Hope that helps

I tried carbing at 35 psi and then serving at 10 psi using 20 ft of 3/16 line and still got too much foam. I am going to reduce the pressure to 25 psi and try again.

Thanks for the advice everyone.

I have made numerous attempts to do what you are trying. Using intermediate pressures is very problematic.

The best results come from either balancing the system for pressure dictated by the vols of CO2 and serving temperature; or, for short term only, by using a shorter, large(r) diameter serving hose, and reducing the pressure and shortening the hose until it does not foam. The shorter the hose, the better.

If you are not going to be able to reliably maintain the temps of the entire serving setup, reducing the pressure is much easier to manage. The pressure only needs to be high enough to just push the product. For long(ish) periods between serving, the pressure will need to be bled from the keg. The product will still stay close to the original carb level for a several hours even with the small losses to CO2 coming out of solution. Colder temps help minimize this effect.

A short, larger diameter hose will reduce foaming significantly. As I mentioned before, the shorter hose, the better. Going too much bigger in one jump than a smaller upstream orifice can sometimes cause cavitation/degassing issues, but 1/4" ID, and even 5/16" ID, seems to work OK for connecting to standard corny dip tubes and QDs.

At low pressures using short hoses, most issues are due to velocity. Just keep reducing the pressure of the reg, and bleeding the keg, to slow down the flow. If you still get foaming at too low flow rates, shorten the hose. If you still have issues, there is a cavitation/degassing site somewhere in the the line.

This approach is backed up by physics. It is no different than why you can pour soda from a bottle, or drink it using a short straw, without it foaming violently.